[X.0] Appendix: Equipment Quick Reference & Index

v2.0.2 / chapter 12 of 12 / 01 jan 07 / greg goebel / public domain

* This appendix provides a very quick summary list of the equipment mentioned in the text, with hyperlinks to the sections of the main text providing more detailed descriptions. Cross references to related items in the list are marked in italics.

Naming systems for World War II electronic gear are a little confusing. The British RAF and Army began with somewhat informal names, such as "AI" for airborne intercept radars, "GL" for gun laying radars, and so on. The Royal Navy had their own type numbers.

The US Army had the "Signal Corps Radio (SCR) designation, while the US Navy generally had two designations, one a letter code such as "FH" and the other a mark designation, such as "Mark 8". The letter code came out of the Navy Bureau of Ships, while the mark designation came out of the Navy Bureau of Ordnance. The whole matter was so confusing that in 1943 the services adopted the universal "Army-Navy (AN)" designation system, for example "AN/APS-4". The "Army-Navy" suffix does not necessarily mean that the gear was used by both services, it just meant they used the Army-Navy designation system.

As several different militaries used type and mark numbers that are easy to confuse, this appendix gives such designations prefixed with an organization code, such as "RN" for "British Royal Navy", "IJA" for "Imperial Japanese Army", and "IJN" for "Imperial Japanese Navy".

[X.1] BRITISH / COMMONWEALTH RADARS

* British / Commonwealth radars included:

• Airborne Intercept (AI) Mark I through Mark IV: Early and inadequate British AI radars, operating at 1.5 meter (200 MHz), with lobe-switching. Only the Mark IV was very satisfactory.

• Airborne Intercept (AI) Mark VII: British 10 cm (3 GHz) AI, derived from prototype "AIS" set. Used conical scanning based on a rotating dish. It was followed by "AI Mark VIII", with fixes and an IFF system.

• Airborne Intercept (AI) Mark IX: British advanced 10 cm (3 GHz) AI, intended to be competitive with the US SCR-720 series, but did not see service until after the war and proved a disappointment.

• Airborne Intercept (AI) Mark X: Designation for the US SCR-720 in British service.

• Air to Surface Vessel (ASV) Mark I & Mark II: Initial "Air to Surface Vessel" longwave radar, operating at 1.5 meters (200 MHz), with lobe switching. ASV.I wasn't very reliable or capable, but ASV.II, which added a side-looking search mode, was a great improvement and used by both Britain and the US.

• Air to Surface Vessel (ASV) Mark III: British 10 cm (3 GHz) ASV radar, based on the H2S bomber targeting radar. Did not reach full production.

• AMES Type 13: British 10 cm (3 GHz) height-finding set, derived from RN Type 277, featuring twin vertically oriented cheese-type antennas and "nodding" operation.

• Chain Home (CH): British floodlight radar, operating around 10 meters (30 MHz), the backbone of British air defense early in the war. Overseas installations were known as "Chain Overseas (CO)". The radar network in its entirety was known as "Home Chain".

• Chain Home Low (CHL): British air warning radar, functionally the same as the 1.5 meter (200 MHz) CD Mark I. Overseas installations were designated "Chain Overseas Low (COL)".

• Coastal Defense (CD) Mark I: British 1.5 meter (200 MHz) coastal defense radar, based on early British AI work, with lobe switching. Used for air warning as CHL and COL.

• Coastal Defense (CD) Mark IV: British 10 cm (3 GHz) coastal defense set, derived from the Type 271 shipboard set, but with larger antennas. Also known as "Type 271 CD" and "Chain Home Extra Low (CHEL)".

• Filter Room: British fighter-control centers, using the Chain Home network.

• Ground Controlled Intercept (GCI) / AMES Type 7: Initial British fighter controller radar operating in the 1.5 meter (200 MHz) band and using a PPI display, derived from CD Mark I.

• Ground Controlled Intercept (GCI) / AMES Type 11: Improved follow-on to GCI / AMES Type 7 fighter controller radar, operating in the 50 cm (600 MHz) band.

• Gun Laying (GL) Mark I/II: British Army longwave gun-laying radar, operating from 5.5 to 3.5 meters (54.6 to 85.7 MHz), capable of providing ranging but only coarse targeting. Copied by the Soviets as the SON-2.

• Gun Laying (GL) Mark 3A: British designation for US SCR-584 10 cm (3 GHz) anti-aircraft radar.

• Gun Laying (GL) Mark 3B: British-built 10 cm (3 GHz) gun-laying radar, with separate transmit and receive antennas.

• Gun Laying (GL) Mark 3C: Canadian-built 10 cm (3 GHz) gun-laying radar, with separate transmit and receive antennas, no automatic tracking. Saw little use.

• H2S: British 10 cm (3 GHz) bomber targeting radar, derived from centimetric "AIS" AI radar prototype.

• LW: 1.5 meter (200 MHz) British Army portable air warning radar. LW was not highly capable, but it was easy to move around and very useful. The Austalians designed a derivative as the "LW/AW".

• Mobile Radar Unit (MRU): British mobile radar, essentially a portable version Chain Home with arrays strung on masts, operating at 7 meters (42.9 MHz).

• Modified Air Warning Device (MAWD): Australian adaptations of the US SCR-268 longwave gun-laying radar to the air warning role.

• Monica: British tail-warning radar.

• RN Type 79/279: British Royal Navy 7.5 meter (40 MHz) shipboard air-warning radar, featuring twin antennas on separate masts, rotating in synchronization.

• RN Type 284: British Royal Navy 50 cm (600 MHz) shipboard gunnery radar, with Yagi antennas and horizontal lobe-switching.

• RN Type 285: British Royal Navy 50 cm (600 MHz) shipboard anti-aircraft radar, similar to RN Type 284.

• RN Type 286: British Royal Navy 1.5 meter (200 MHz) shipboard radar, derived from early AI work. The early Type 286M had a fixed antenna, while the improved Type 286P had a steerable antenna.

• RN Type 271: Early British Royal Navy shipboard 10 cm (3 GHz) set, with separate transmit and receive cheese-type antennas stacked on top of each other. Manual direction, no PPI.

• RN Type 273: Improved derivative of RN Type 271 set for major warships, operating at 10 cm (3 GHz), with 90 centimeter (1 yard) transmit and receive antennas and a gyrostabilized mounting. Manual direction, no PPI.

• RN Type 277: Improved version of RN Type 273, operating at 10 cm (3 GHz). Initial versions used dual cheese-type antennas.

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[X.2] OTHER BRITISH / COMMONWEALTH EQUIPMENT

* Other British / Commonwealth equipment included:

• Abdullah: British radar homing system, carried on Hawker Typhoons, saw little use.

• Angel: Codename for a radar corner reflector.

• Airborne Cigar: British aircraft-based radio-channel jammer.

• Airborne Grocer: British airborne broadband noise jammer, operating on German Lichtenstein AI frequencies. A ground-based version, "Ground Grocer", proved ineffective.

• Boozer: British radar warning receiver, used on bombers. Little used in practice since it tended to produce many false alarms.

• Carpet: Allied noise jammer, operating on Wuerzburg frequencies, with different versions built the US and Britain. Followed by the improved British "Carpet II", with frequency agility to prevent "home on jam".

• Chaff: Aluminum strips dropped from aircraft to jam radar, including Window to jam Wuerzburg and Rope to jam Freya.

• Corona: British ground-based radio-channel deception network, used to disrupt the German air-defense communications system.

• Decca Navigator: British longwave hyperbolic navigation system, also known as "QM" or just "Decca", operating at kilometer wavelengths. Little used during the war, but persisted in operation for decades afterwards.

• Gee: British hyperbolic navigation system, using stations with three separated transmitters, with one "master" and two "slaves", operating in the band from 15 to 3.5 meters (20 to 85 MHz). The name was short for "Grid". Gee was the conceptual ancestor of LORAN.

• Gee-H: British navigation system, conceptually similar to Oboe but with radio interrogators in aircraft and radio transponders at the base stations, not the other way around. Based on Gee gear and operated around 15 to 3.5 meters (20 to 85 MHz).

• Ground Cigar: British ground-based radio-channel jammer.

• High Frequency Direction Finding (HF/DF): "Huff-Duff", as it was known, was carried on Allied escort vessels to locate and help hunt down German submarines.

• IFF Mark I/II: First true IFF units. IFF Mark I was triggered by Chain Home pulses, while IFF Mark II could respond to COL and GL signals as well.

• IFF Mark III: Definitive Allied IFF with its own interrogation band.

• Lucero: British "home on jam" device to zero in on German Kettenhund jammer transmissions.

• Mandrel: Allied broadband noise jammer, operating on Freya frequencies. Different versions were built by Britain and the US.

• Moonshine: British pulse-repeater deception jammer, operating on Freya frequencies.

• Oboe: British remote targeting system, using two radar stations designated "Cat" and "Mouse", and a radio beacon in the bomber being guided. The Cat radar tracked the bomber at a constant radius, transmitting a tone that changed in frequency if the bomber drifted off the radius, which is why the system was known as "Oboe". The Mouse radar determined when the bomber was over the target and sent a release signal.

  Mark I Oboe operated in the 1.5 meter (200 MHz) range, while Mark III Oboe operated in the 10 cm (3 GHz) range.

• Ping Pong: British ground-based radar location network.

• Pip Squeak: Early British attempt at IFF, involved ground tracking of a fighter through its radio. Clumsy and quickly abandoned.

• Rebecca / Eureka: Allied radar beacon system, operating on 1.5 meters (200 MHz) with Rebecca as interrogator and Eureka as beacon.

• Rope: Chaff cut to 1.7 meter (5 feet 6 inches) to jam German Freya search radars.

• Serrate: British radar homing device, used by British night fighters to home on German night fighters through their Lichtenstein AI emissions.

• Shiver: British broadband noise jammer, operating on Wuerzburg frequencies.

• Tinsel: Early British fighter-control radio channel noise jammer, used microphones in a bomber's engine nacelles to produce audio noise.

• Window: Chaff cut to 30 centimeters (1 foot) to jam German Wuerzburg targeting radars.

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[X.3] US RADARS

* US radars included:

• AN/APG-15: 12 cm (2.5 GHz) tail turret fire-control radar with conical scanning and automatic tracking, used on B-29 Superfortress bomber.

• AN/APN-1: Low-altitude radar altimeter.

• AN/APS-6: Improved follow-on to the US Navy ASH or AN/APS-4 with a simple "gunsight" type display to allow it to be used in single-seat fighters.

• AN/APS-10 Little Abner: Ground-based version of the USN Mark 22 height-finder radar.

• AN/APS-13: Tail-warning radar for fighters.

• AN/APS-16 & AN/APS-17: Tail-warning radar for bombers.

• AN/APS-20: US Navy 3 cm (10 GHz) airborne early warning radar, carried under TBM-3W Avengers for fleet protection.

• AN/TPS-1: Lightweight US tactical air-warning radar, operating at 24 cm (1.25 GHz).

• ASB: US Navy ASV radar, a lightweight longwave 58 cm (515 MHz) set used on various attack aircraft, originally designated "XAT". It featured Yagi antennas under each wing.

• ASD (AN/APS-3): Also known as "Dog", US Navy ASV radar, a 3 cm (10 GHz) set carried on a single-engine aircraft such as the Grumman Avenger Torpedo bomber.

• ASE: US Navy radar, a copy of the British ASV Mark II, used on Consolidated PBY Catalina flying boats early in the war.

• ASG (AN/APS-2): Also known as "George", a US Navy 10 cm (3 GHz) ASV set with PPI display.

• ASH (AN/APS-4): US Navy 3 cm (10 GHz) ASV radar, also useful for AI work.

• CXAM: Early 1.5 meter (200 MHz) US Navy shipboard warning radar, derived from NRL prototype "XAF" radar and built by RCA, in preference to the company's "CSZ" prototype. Manual direction, no PPI, maximum range for aircraft about 80 kilometers (50 miles).

• Eagle (AN/APQ-7): US Army 3 cm (10 GHz) bombing radar, using an electronically steered dipole array in the form of a wing carried under the fuselage of a B-29. Used in bombing raids against Japan.

• FA: Early US Navy shipboard gunnery radar built by Bell Labs, operating at 40 cm (750 MHz), originally designated "CXAS".

• FC: US Navy shipboard 10 cm (3 GHz) gunnery radar, also known as "USN Mark 3", with horizontal lobe switching.

• FD: US Navy shipboard 40 cm (750 MHz) anti-aircraft radar, also known as "USN Mark 4", with horizontal and vertical lobe switching.

• FH: US Navy shipboard 3 cm (10 GHz) surface fire control radar, using a phased-array antenna. Also known as "USN Mark 8", and was both the first operational Allied phased-array radar and the first microwave phased-array radar.

• FJ & FL: Short-range shipboard targeting radars, also known as "Mark 9" and "Mark 10".

• H2X (AN/APS-15): US 3 cm (10 GHz) bomber targeting radar built by Philco, also known as "Bombing Through Overcast (BTO)" or "Mickey". It was also fitted with a different antenna to be used as an ASV radar. B-29s carried a variant with a bombing computer, designated the "AN/APQ-13".

• Low Altitude Bombing (LAB or AN/APQ-5): Radar bombsight that could be integrated with various radars and used for low-altitude antiship attack.

• Microwave Early Warning (MEW or AN/CPS-1): "Microwave Early Warning" 3 cm (10 GHz) radar, with back-to-back rotating curved "billboard" antennas. Used in conjunction with the AN/APS-10 Little Abner height-finder radar, since MEW was only accurate in the horizontal plane.

• SA: Small-sized version of the 1.5 meter (200 MHz) SK surface search radar.

• SC: Mid-sized version of the 1.5 meter (200 MHz) SK surface search radar.

• SCR-268: Early US Army gun-laying and searchlight-direction radar, built by Western Electric. The SCR-268 operated at 1.5 meters (200 MHz) and had vertical and horizontal lobe switching.

• SCR-270: US Army mobile longwave air-warning set, built by Westinghouse, operating at 3 meters (100 MHz) and without lobe switching.

• SCR-271: Fixed-site version of the 3 meter (100 MHz) US Army SCR-270 mobile air-warning radar.

• SCR-516: Modification of US Army SCR-268 gun-laying radar for low-altitude air warning, provided with PPI display.

• SCR-517: US Army modification of the 10 cm (3 GHz) SCR-520 AI radar for ASV.

• SCR-520: Initial US Army 10 cm (3 GHz) AI, built by Western Electric, saw little or no use.

• SCR-521: US version of British ASV.II.

• SCR-527: US copy of British GCI / AMES Type 7 1.5 meter (200 MHz) fighter-controller radar, saw little or no use.

• SCR-540: US Army copy of British 1.5 meter (200 MHz) AI Mark IV, saw little or no use.

• SCR-545: US Army gun-laying system developed by Bell Labs, featuring both 10 cm (3 GHz) and 1.5 meter (200 MHz) radar with automatic tracking. The SCR-545 was not produced in quantity.

• SCR-581: Early US Army radio altimeter system.

• SCR-582: Coastal defense version of the US Navy 10 cm (3 GHz) SG shipboard search radar.

• SCR-584: US Army 10 cm (3 GHz) anti-aircraft radar, integrated with an analog computer designated the "M-9 Predictor-Corrector Unit" to automatically track targets.

• SCR-602: US built version of British 1.5 meter (200 MHz) LW portable early-warning radar.

• SCR-717: Improved version of SCR-517 10 cm (3 GHz) ASV radar.

• SCR-718C: Improved follow on to SCR-581 radar altimeter.

• SCR-720: Major US nightfighter radar, operating at 10 cm (3 GHz), used on Northrop P-61 Black Widow.

• SD: US Navy 2.45 meter (122 MHz) submarine warning set, very crude, only capable of providing an alert that an intruder was in the area.

• SF: Lightened version of US Navy 10 cm (3 GHz) SG shipboard search radar.

• SG: US Navy 10 cm (3 GHz) shipboard search radar built by Raytheon, with rotating antenna, PPI display, and gyrostabilized mount.

• SJ: US Navy 10 cm (3 GHz) submarine warning radar, with rotating antenna and PPI.

• SK: Improved and very successful version of the US Navy 1.5 meter (200 MHz) CXAM, with a rotating antenna and PPI display. Known as the "Flying Bedspring".

• SM: US Navy 10 cm (3 GHz) height-finding and fighter direction radar, used on carriers as a complement to the SK.

• SP: Shipboard version of SCR-584 10 cm (3 GHz) anti-aircraft radar on a stabilized mount.

• SS: US Navy 3 cm (10 MHz) submarine warning radar, a follow-on to the SJ.

• USN Mark 12: Improved version of FD / USN Mark 4 anti-aircraft radar, incorporating a USN Mark 22 height finder and automatic tracking.

• USN Mark 22: USN Navy 3 cm (10 MHz) height-finding radar with "orange slice" antenna and "nodding" operation. Used as an element of the USN Mark 12 anti-aircraft fire control radar.

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[X.4] OTHER US EQUIPMENT

* Other US equipment included:

• AN/APN-2 & AN/PPN-1: American copies of British Rebecca & Eureka radio beacon system.

• AN/APR-2: Wideband automatic scanning SIGINT receiver.

• AN/CRT-1A: Early US sonobuoy.

• AN/TRC-1: US radio relay system, providing 1 voice channel or four teletype channels, operating at 4.29 to 3 meters (70 to 100 MHz). Followed by improved "AN/TRC-2" and "AN/TRC-4", and then the "AN/TRC-5" and "AN/TRC-6" with more channels.

• Distance Measurement Equipment (DME): Modern range-finding radio transponder system, used with VOR to form "VOR/DME", and as an element of TACAN.

• Archies: Radar proximity fuze for the US atomic bombs, based on AN/APS-13 tail-warning radar.

• Combat Skyspot: Vietnam-era ground-based radar precision bombing system along the general lines of Oboe.

• Ground Controlled Approach (GCA): Radar-based landing system, with a ten-centimeter search set with a PPI for tracking aircraft near the airfield, and two three-centimeter fine-positioning sets, one to determine the elevation angle of the aircraft, and the other to determine its sideways deviation from the proper approach path. An analog computer determined the aircraft's approach path, and the aircraft was guided in to the runway by a ground controller using voice radio.

• Instrument Landing System (ILS): Commercial landing system introduced in 1937, and put in common use after World War II. ILS used a "right-left" signal in the 108 to 112 MHz range and a "glide slope" signal in the 329 to 335 MHz range.

• Joan / Eleanor: Narrow beam portable radio system for secret communications with spies, operating at 1.15 meters (260 MHz).

• Long Range Navigation (LORAN): US hyperbolic navigation system, using stations with two separated transmitters, designated "master" and "slave". The initial "LORAN-A" operated in four bands in the vicinity of 160 meters (1.88 MHz), while the postwar "LORAN-C" operated around 3,000 meters (100 kHz). The US military also used a short-range, portable, higher accuracy system known as "LORAN-D" in the postwar period.

• Magnetic Anomaly Detector (MAD): Sensor system carried on Alllied aircraft that could detect disturbances of the Earth's magnetic field caused by a submerged submarine.

• Omega: Postwar US global hyperbolic navigation system, operating at about 30 km (10 kHz). Often used as a complement to the VLF navigation system.

• S-27: Commercial wideband radio receiver built by Halicrafters, used in ferret missions.

• SCR-194: US backpack AM radio, operating over 10.9 to 5.75 meters (27.5 to 52.2 MHz). Followed by similar "SCR-195", operating over 5.77 to 4.62 meters (52 to 65 MHz).

• SCR-300: US backpack FM radio, operating over 7.5 to 6.25 meters (40 to 48 MHz).

• SCR-508: US FM radio for vehicles, operating over 15 to 10.75 meters (20 to 27.9 MHz). Followed by similar "SCR-608", operating over 11.1 to 7.71 meters (27 to 38.9 MHz).

• SCR-522: British-designed US VHF AM radio for aircraft, with four channels, operating over 3 to 1.92 meters (100 to 156 MHz).

• SCR-536: US AM "handie-talkie" radio, operating over the 85.7 to 50 meter (3.5 to 6 MHz) range.

• SCR-587 (ARC-1): Wideband SIGINT receiver.

• Short Range Air Navigation (SHORAN): Range-finding radio transponder system introduced late in the war, led to DME.

• Tactical Air Navigation (TACAN): Modern radio navigation system, consisting of a radial direction radio beacon coupled with DME.

• VHF Omni-Range (VOR): Modern radial direction radio beacon, generally used with DME to form "VOR/DME".

• VLF: Modern US Navy global communications system to send short messages to submarines underwater, operating at about 30 km (10 kHz), often used as a complement to Omega as a hyperbolic navigation system.

• VT: Designation for US-built proximity fuze.

• XARD: Early crude wideband SIGINT receiver.

• YE / YG: US Navy carrier-based homing beacons.

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[X.5] GERMAN RADARS

* German radars included:

• Berlin: German 10 cm (3 GHz) AI, much too little and too late. Its successor, "Bremen", never reached production.

• Egerland: German 10 cm (3 GHz) ground fire-control system, with a search radar named "Marbach" and a targeting radar named "Kulmbach".

• Elefant-Ruessel: Odd and backward German "floodlight" radar system, used for tracking V-2 rocket tests.

• Freya: German ground-based early-warning radar built by GEMA, with a steerable antenna and operating at 2.4 meters (125 MHz).

• Himmelbett (Four Poster Bed): German night-fighter direction station, with a Freya search radar and two Wuerzburg-Riese tracking radars.

• Hohentweil: German ASV radar operating at 50 cm (600 MHz).

• Jagdschloss (Hunting Lodge): German ground-based wide-area search radar, operating around 2 meters (150 MHz). First German radar with PPI.

• Klein Heidelberg: Unusual German "passive" radar, picked up direct Chain Home emissions and used a directional antenna to spot echoes from them.

• Lichtenstein B/C: German AI radar operating at 50 cm (600 MHz) with "X"-style antennas, carried on Me-110 and Ju-88 night fighters.

• Lichtenstein SN2: Improved Lichtenstein, operating around 4 meters (75 MHz) with "Elk Antlers" antennas, had some resistance to window. Often used along with a Lichtenstein B/C set, with a single X-style antenna mounted between the four Elk's Antlers sets.

• Mammut (Mammoth): German ground-based fixed-position early warning radar, consisting of 16 Freya antennas linked together. The entire Mammut array was 30 meters across and 10 meters high (98 by 33 feet), and the radar had a range of 320 kilometers (200 miles). Mammuts were often set up back-to-back to improve coverage.

• Mannheim: Improved German gun-laying radar, a follow-on to Wuerzburg with greater range and accuracy. Late production had automatic target tracking.

• Neptun: German longwave AI follow-on to Lichtenstein series, with shorter minimum range of about 100 meters (330 feet), and other improvements. Saw little use.

• Seetakt: German shipboard warning radar built by GEMA, with a steerable array and operating at 80 cm (375 MHz) in production units. Also used in fixed-array coastal-defense sets.

• Wassermann (Waterman): German ground-based early-warning radar, based on eight or more Freyas mounted vertically on a rotating tower 60 meters (190 feet) high. Had a range of 240 kilometers (150 miles) and good height-finding capabilities.

• Wuerzburg: German gun-laying radar built by Telefunken, with steerable dish antenna, helical scanning, and an operating band around of 50 cm (600 MHz).

• Wuerzburg-Riese: German longer-range version of Wuerzburg, with bigger dish but the same electronics.

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[X.6] OTHER GERMAN EQUIPMENT

* Other German equipment included:

• Erstling (Firstborn): German IFF system, responded to 2.4 meter (125 MHz) Freya signals. German ground radars operating at other frequencies used an interrogator named "Kukuck (Cuckoo)" to operate with Erstling. German night-fighters did not have interrogators.

• Flammen (Flames): Night-fighter device for homing in on Allied Mark III IFF.

• Flensburg: Night-fighter device for homing in on British Monica tail-warning radar.

• Freya-laus: German counter-countermeasures mod for Freya and Mammut radars, using Doppler tracking to sort out bombers from chaff.

• Kammhuber Kinos (Kammhuber Cinema): German night fighter control center.

• Karl: German ground-based longwave radar jammer.

• Kettenhund: German airborne longwave radar jammer.

• K-laus: Advanced German counter-countermeasures scheme for the Wuerzburg radar, combined Doppler tracking with filtering.

• Knickebein (Crooked Leg): Improved version of Lorenz landing system for bomber targeting, with two transmitters set up at different locations, operating at 10 meters (30 MHz) as with Lorenz. The bomber flew out from the transmitter along one beam, instead of inward as with Lorenz, and listed for the second beam, which intersected the first over the target. The error was a few hundred meters at the maximum distance, which was limited by the line of sight.

  Formally known as "X-Leitstrahlbake (Direction Beacon)", with the name Knickebein adopted due to the bent appearance of the primary transmitting antenna. The British developed jammers named "Aspirins" to jam the Knickebein signals.

• Korfu: Centimetric radar warning system, similar to Naxos, but provided better homing capability.

• Lorenz: German commercial blind-landing system from 1934, which operated at 10 meters (30 MHz) and sent out one beam carrying Morse-code dashes next to another beam with dots. It actually used a single transmitter with two antennas, with the transmitter shunted back and forth between the two using an electromechanical cam-based switch. A pilot approaching the transmitter would move in between the two beams until they became a continuous tone at their centerpoint. Effective range was about 100 kilometers (60 miles).

• Metox: German longwave radar warning receiver carried on submarines, using a stowable antenna known as the "Cross of Biscay".

• Naxburg: Naxos centimetric radar warning receiver mated to Wuerzburg radar dish to track bomber formations. Used by the German Y-Dienst system.

• Naxos: Night-fighter device for homing in on 10 cm (3 GHz) radar emissions. Also used on submarines and with Wuerzburg sets.

• Sonne (Sun): German radio beacon system that provided compass information. Known as "Consol" to the Allies and used after the war.

• Stendal: German "home on jam" system, too inaccurate to be useful.

• Taunus: German counter-countermeasures mod for Wuerzburg radar, using filtering to sort out persistent radar returns from transient ones.

• Wasserfloh: German counter-countermeasures mod for Wassermann radar, using Doppler tracking to sort out bombers from chaff.

• Wilde Zau (Wild Sow) ): Luftwaffe night fighter technique in which day fighters attempted to intercept bombers by flying above a bomber stream to see the targets lit up by the burning city below. Effective but hazardous due to landing accidents.

• Wizmar: German counter-countermeasures mod for Wuerzburg, allowed rapid changing of operating band.

• Wuerzlaus: German counter-countermeasures mod for Wuerzburg radar, using Doppler tracking to sort out bombers from chaff.

• X-Geraet (X-Device): An evolution of Knickebein, featuring a much smaller antenna, operating at 5 meters (60 MHz) instead of 10 meters (30 MHz), and using a needle indicator instead of a tone to track the beam. The bomber rode up one beam as before, but since the simpler antenna produced a number of side beams, the crew had to pass through multiple beams from the second transmitter, using them as "checkpoints" to monitor their approach to the target. X-Geraet was also referred to as "Wotan 1" by the Germans. The British developed jammers named "Bromides" to jam X-Geraet signals.

• Y-Dienst: German signals intercept organization, used passive systems to track bomber formations.

• Y-Geraet (Y-Device): An evolution in turn of X-Geraet, using a single transmitter instead of two antennas. The antenna transmitted on two frequencies, with the bomber retransmitting one of the signals on a slightly different frequency. The phase shift of the difference between the transmitted and retransmitted frequency was used to determine the range of the bomber, with the bomber told when to drop their bombs by the Y-Geraet site. The Germans also called Y-Geraet "Wotan 2". The British used TV transmitters to jam Y-Geraet transmissions, and later developed more specialized jammers.

• Zahme Sau (Tame Sow): Luftwaffe night fighter technique in which pilots were vectored into a bomber stream to find targets on their own.

• Zwilling (Twin): Unsuccessful German IFF system, responded to 50 cm (600 MHz) Wuerzburg signals.

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[X.7] JAPANESE RADARS

* Japanese radars included:

• IJA Tachi 1 / Tachi 2 / Tachi 4 / Tachi 31: IJA derivatives of US SCR-268, all operating at 1.5 meters (200 MHz). Only the Tachi 31 was produced in any quantity.

• IJA Tachi 3: Derivative of British GL longwave gun-laying radar, operating at 3.75 meters (80 MHz).

• IJA Tachi 6: Initial Japanese Army air-warning radar, a floodlight system operating at 4 meters (71.4 MHz).

• IJA Tachi 7 / Tachi 18: Transportable derivatives of the IJS Tachi 6.

• IJA Tachi 20 / Tachi 35: Japanese Army height finder radars, too little and too late.

• IJA Take 1: Japanese Army 2 meter (200 MHz) ASV radar.

• IJN Mark I Model 1: Initial Japanese Navy ground-based air-warning radar, operating at 3 meters (100 MHz).

• IJN Mark I Model 2 / Mark I Model 3: Transportable versions of the IJN Mark I Model 1.

• IJN Mark II Model 1: Initial Japanese Navy shipboard radar, operating at 1.5 meters (200 MHz).

• IJN Mark II Model 2: Japanese Navy 10 cm (3 GHz) shipboard radar, with conical transmit and receive antennas.

• IJN Mark II Model 4: Japanese Navy 1.5 meter (200 MHz) lightweight radar, for service on small vessels and submarines.

• IJN Mark IV Model 1 / Mark IV Model 2: Japanese Navy derivative of the US Army SCR-268 gun-laying radar, operating at 1.5 meters (200 MHz).

• IJN Mark VI Model 2: Japanese Navy 2 meter (200 MHz) ASV radar.

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